Containers, such as for example, beverage bottles, are normally examined for the presence of damage and/or foreign particles prior to the filling of the product. It is known, for example, from EP 0663069 B1 to image the side wall of empty bottles in bright field from multiple circumferential directions using a camera and a mirror cabinet. Due to light refraction at the curved boundary surfaces between the bottle wall and the air, however, it is necessary for purposes of exposure to use comparatively wide surface-emitting lamps, which causes an undesirably excessive need for space. Moreover, surface-emitting lamps and cameras for the sidewall inspection must be arranged opposite one another transverse to the transport direction. In order to image containers in their entirety, at least two such inspection units must then be provided, one behind the other. In favor of an optionally compact design of the inspection units, the containers are also rotated about their main axis between the former. This results in additional complexity.
In other inspection units, such as for inspecting the bottom of empty bottles, the problem occurs that in the case of irregular shapes, such as for example behind recessed grips, a directional bright field irradiation of each wall area is hampered or, in part, impossible. Where wall areas to be inspected are shaded, reliable inspection of the empty bottles is impossible or possible only to a limited extent.
There is a need therefore for alternative methods of inspection and inspection devices in which the aforementioned problems do not occur, or occur in only a milder form.